Surgical knife blades mountable in holders for use have long been known. The holders were typically made of metal into which the knife blade was inserted before use and from which the knife blade was removed after use.
With the development of plastics, disposable plastic blade holders were developed with surgical knife blades mounted thereon, ready for use. However, in order to prevent inadvertent contact with the blade before use, some sort of protective cover was required. Cardboard or other tubing, for example, was provided to be placed about the blade during transportation and again for disposal.
There is shown in German Patentschrift No. 2 058 903 a blade holder including a snap-off protective shield integrally formed with the holder and arranged to be removed before use. This shield serves to protect persons handling the holder from contacting the blade before it is used, the shield being thrown away after being removed. Thus, it provides no protection for the used blade at the time of disposal, which can cut the disposal plastic bag or the user when discarded.
There is shown in U.K. Pat. No. 848,388 a cutting tool having a blade supported in a handle, and a sheath enclosing the cutting edge of the blade moulded onto the blade by insert molding and attached to the handle by a readily frangible connection therewith. The sheath is removed by rotating it about the blade and breaking the connection to the handle. There is no suggestion of using the sheath again after use of the cutting tool and, due to the nature of the insert molding process and the bond formed thereby, the sheath of this patent can not physically be replaced on the blade once it is removed.